Cooling system for electrical apparatus



1,643,014. Sept. 20, 1927. B. HODTUM COOLING SYSTEM FOR ELECTRICAL APPARATUS Filed Dec. '7. 1925 Patented Sept. 20, 1927.

UNITED STATES PATENT OFFICE.

JOSEPH BEBNEARDT HODTUM, OF BELLEVUE, PENNSYLVANIA, ASSIGNOB TO PITTS- BUBGH TRANSFORMER COMPANY, A CORPORATION 01' PENN COOLING SYSTEM FOR ELECTRICAL APPARATUS Application filed December 7, 1925. Serial No. 73,697,

This invention relates to a cooling system for electrical apparatus and particularly to such a system for transformers submerged in oil in a containin tank.

The object of the invention is to provide a system which will utilize a supply of cooling fluid to control the temperature of the apparatus at loads above a'predetermined amount and automatically continue the cooling after the load has been reduced. This permits the transformer to be self cooled at low loads and econo-mizes the supply of cooling fluid by confining it to higher loads and to the reduction of the tempera-- tures resulting from said higher loads.

Prior systems for controlling the flow of cooling liquid in combined self and water cooled transformers have depended on the temperature of the to oil or upon load conditions to open or c ose the coolin water supply. If the water is controlled y temperature means the oil Wlll be mamtamed at some uniform temperature and if this temperature is kept low Water will flow through the cooling system almost continuously and thus be largely wasted; or if such a system is set for a high temperature the oil will rapidly sludge and deteriorate. On the other hand the systems depending on the :3 load for the control of the water start the flow as soon as the load demands it and stop the water as soon as the load is reduced and therefore leave the transformer at a relatively high temperature for long periods of time.

The system of this invention overcomes the objections to these prior systems in that it starts the auxiliary cooling water when the load demands it but flow until the transformer has cooled down to a desired temperature.

The accompanying drawing shows the system of this invention diagrammatically in connection with a transformer.

In the system shown the transformer 1 is in a body of oil 2 in a tank 3 and this oil is cooled both by radiation from the walls of the tank and by a cooling fluid circulating through the cooling coil 4. Up to a certain load on the transformer the-self cooling through radiation from the walls. 3 would be suiiicient to maintain the desired temperature and at higher loads a circulation of cooling fluid will be set up through the coil 4.

does not stop the.

upward when the circuit is closed and thus in turn closes across the contacts 12 to complete the circuit through the solenoid 13 and open the water valve 14 to supply water to the cod 4' The upward movement of the magnetlc contactor 11 also closes a set of auxiliary contacts 15 which bypass the contacts 9 of relay 7 and thus hold the contactor 11 closed regardless of the operation of the load until the thermostat contact 10 opens the circuit and releases the contactor 11 and thus breaks the circuit through the SOl8I101d 13 and causes the valve 14 to close and shut off the water supply.

Wlth this system the water through the coil 4 can be started at any desired oint of the self cooled rating, for instance eighty percent and thus add to the self cooling the water cooling for all higher loads and until the temperature of the transformer has been reduced to the desired amount as determined by the setting of the thermostat 10.

Since the thermostat 10 is in series with the contacts 9 of the relay 7 the water through the coil 4 will not start unless the temperature of the transformer is above the thermostat setting. The transformer of this system will operate fully as a self cooled unitfor all loads lower than the water cooled rating, and just as soon as the load gets into the water cooled range water is started through the water cooling system unless the temperature of the transformer, as determined by the setting of the thermostat 10, is not sufiiciently high to necessitate water cooling. When, however, both the load and the temperature of the trans former require the water cooling and the flow through the coil 4 has been started, this flow will not be stopped until the desired reduction in temperature has been effected, no matter what the changes in the load may be. The oil in the transformer is, therefore, not held at any standing temperature except a very low one as set by the thermostat- 10, for instance, under f10 (J. by a thermometer, and at the same time the water through the coil 4 is not run continuously but is only used in sufficient quantity to maintain the temperature within the desired limits during the load operation and continued long enough to qulcldy reduce the temperature when the load is reduced.

The current through the thermostat and magnetic contactor may be provided by a small transformer 16 with the primary connected. across the line and the secondary developing for instance ten to fifteen volts.

Similarly the circuit for the solenoid 13 may be supplied with current from any convenient A. C. or D. C. source. WVhile the system of this invention has been described in connection with a specific embodiment thereof, the invention is not confined to these particular circuits but is intended to cover any modification thereof withln the scope of the appended claims.

I claim:

1. In a cooling system the combination with electrical apparatus immersed in oil in a container adapted to radiate heat to cool said oil. of means for circulating an auxiliar cooling fluid within said container comprising valve means and a control therefor adapted to open said valve upon the occurrence of predetermined load conditions and to close said valve upon the occurrence of predetermined temperature conditions comprising a switch device actuated by the load current and a co-operating temperature operated thermostat switch.

2. In a cooling system the combination with electrical apparatus immersed in oil in a container adapted to radiate heat to cool said oil, of means forcirculating an auxiliary cooling fluid within said container comprising valve means and a control therefor adapted to open said valve upon the occurrence of predetermined load conditions and to close said valve upon the occurrence of predetermined temperature conditions comprising a switch device actuated by the load current and a eo-operating temperature operated thermostat switch in series with each other.

3. In a cooling system the combination with electrical apparatus immersed in oil in a container adapted to radiate heat to cool said oil, of means for circulating an auxiliary coolin fluid within. said container comprising va ve means and a control therefor adapted to open said valve upon the occurrence of predetermined load conditions and to close said valve upon the occurrence of predetermined temperature conditions comprising a switch device actuated by the load current and a oo-operating temperature operated thermostat switch in series with each other, and means for short circuiting said current actuated switch so that the control circuit will not be broken until the thermostat operated switch opens.

4. In a cooling system the combination with electrical apparatus immersed in oil in a container adapted to radiate heat to cool said oil, of means for circulating an auxiliary cooling fluid within said container comprising valve means and a control therefor adapted to open said valve upon the occurrence of predetermined load and temperature conditions and to close said valve only upon the occurrence of predetermined temperature conditions comprising a switch device actuated by the load current and a cooperating temperature operated thermostat switch.

5. In a cooling system the combination with electrical apparatus immersed in oil in a container and having means for circulating a cooling fluid within said container,

valve means for said cooling fluid, and a control for said valve means comprising a thermostat and a load controlled circuit, and connecting means between said thermostat and circuit and valve combining said load control and thermostat in series so that said valve will be normally closed and will open only when the temperature at said thermostat and the load at the load control both exceed predetermined minimums.

6. In a cooling system for electrical apparatus, means for cooling said apparatus, means for rendering said cooling means effective in response to a joint rise to predetermined minimums of the load on said apparatus and the temperature thereof respectively, and means for rendering said cooling means ineffective in response to a drop in said temperature below a predetermined minimum, irrespective of the load on said apparatus.

7 In a cooling system for electrical apparatus, means for cooling said apparatus, means responsive to the load on said apparatus, means responsive solely to the temperature of said apparatus, and means responsive to joint effective operation of said load and temperature responsive means for controlling said cooling means.

8. In a cooling system for electrical apparatus, means for cooling said apparatus, means responsive to the load on said appa ratus, means responsive solely to the temperature of said apparatus, means responsive to joint effective operation of said load and temperature responsive means for increasing the effect of said cooling means, and means whereby the effect of said cooling means is decreased solely by said apparatus-temperature responsive means.

JOSEPH BERNHARDT HODTUM. 

